The digital printing of textiles is a large and growing business market. To meet the needs of this market, pigment dispersants and binders that disperse and durably bind pigments to a variety of fabric surfaces are required. Polymeric dispersants are widely used to stabilize pigments in ink jet printing inks. The dispersant serves to form a shell around the pigment particle, preventing flocculation and coagulation. Additionally, polymer-based binders may be added to the ink composition to enhance the binding of the pigment to the fabric surface.
Proteins and peptides have also been used as dispersants and film-forming binders in coloring compositions. For example, Brueckmann et al. in U.S. Pat. No. 5,124,438 describe the use of chemically modified proteins, such as casein, collagen, albumin and gelatin, as dispersants in color formulations. Additionally, cellulose binding domains (CBDs) from various enzymes, such as cellulases, xylanases, mannanases, arabinofuranosidases, acetyl esterases, and chitinases, have been used in compositions for treating cellulosic fabrics to ensure the deposition of a benefit agent onto the fabric (Jones et al. in WO 9800500 and Smets et al. in WO 01/18897). Mimic CBDs, which are synthetic peptides of 30 or fewer amino acids, preferably containing at least three aromatic amino acids, have also been used to link various benefit agents to cellulosic fabrics (Bjorkquist et al., WO 0132848).
Han et al. (Shengwu Huaxue Yu Shengwu Wuli Xuebao 30:263-266 (1998)) describe the identification of peptides that specifically bind to a cellulose matrix using phage display screening. The deduced amino acid sequences of these cellulose-binding peptides have a conserved aromatic residue, tyrosine or phenylalanine, which is similar to the normal cellulose-binding domain of cellulose-binding proteins. The use of these cellulose-binding peptides in new dispersants and/or binders for coloring applications is not described in that disclosure.
Nomoto et al in EP1275728 describe the identification of pigment-binding peptides using phage display. Some carbon black, copper phthalocyanine, titanium dioxide, and silicon dioxide-binding peptide sequences are disclosed. However, the use of the pigment-binding peptides as dispersants and/or binders for coloring applications is not described.
O'Brien et al. in copending and commonly owned U.S. patent application Ser. No. 10/935,254 and U.S. Application Publication No. 20050054752 describe peptides, identified by phage display screening, that bind with high affinity to pigments and print media. The peptides were used to prepare diblock and triblock dispersants and/or binders that provide improved durability for coloring applications. However, improved dispersants and/or binders that provide greater durability, particularly for textile fabric printing, are still required.
Therefore, the problem to be solved is to provide pigment dispersant and/or binders that effectively disperse pigments and provide improved durability to meet the demanding-needs of more advanced, high quality coloring applications, such as textile printing.
Applicants have addressed the stated problem by discovering that the addition of at least one positively charged amino acid residue at the N-terminal and/or C-terminal end of the sequence of a peptide having binding affinity for pigment or substrate surfaces significantly enhances the strength of the interaction of the peptide with substrate surfaces. These affinity peptides having at least one terminal positively charged amino acid residue function as pigment dispersants and/or binders that provide significantly improved durability on textile fabrics compared to conventional polymeric dispersants and binders or the unmodified affinity peptides.